he is the boyfriend of a woman who has lived on the same estate for about 20 years...he moved in with her about 6 months ago...maybe more....he's in his 40s and a few months ago a woman reported that he was flashing her...naked in the window....he then sent some letters to a few women...one or two each over a period...inoccuous stuff like "You've got nice legs" and "we could go out" kind of stuff but worrying given the flashing....I never heard about all this but my sister just told me that Mum hass recived two letters from him last week inviting her swimming "I'll wear my trunks" 
ANd my Mum is in her 60s and has not been well at all lately...she doesn't need this.
The police have been to speak to him and warn him but apparently can do nothing until he sends three letters! Only then is it harrasment and only then can they serve something officially.
Mum has just had extra locks put on by the police but they say he has no record of sexual assault....what the eff can I do?? Short of marching round there and demanding the silly woman whois harbouring him to kick him out!